Improving the manufacturability of floor slabs by pre

Improving the manufacturability of floor slabs by pre-installing elements that partially replace reinforced concrete and formwork

Seyran Akimov * , Olga Balakchina, Elvira Akimova, Vladimir Malahov and Vasilij Shalenny

Crimean Vernadsky Federal University, 295493, Simferopol, Republic of Crimea, Russia

Abstract. The article discusses well-known and perspective constructive

and technological systems for the installation of monolithic and precast-

monolithic floor slabs of civil and industrial buildings. It shows examples

and expediency of using all kinds of inserts made of plastic and other light

materials and products for replacing a part of heavy monolithic reinforced

concrete. An original resource-saving method for the installation of

precast-monolithic floor slabs with a simultaneous increase in the degree of

their construction readiness is proposed. This effect is achieved by

reducing their own weight and the use of permanent formwork. Reduction

in own weight of the precast-monolithic floor slab is ensured by the use of

volumetric lightweight trapezoidal or rectangular inserts, preferably made

of expanded polystyrene, during its installation. The use of permanent

formwork will eliminate the need for the subsequent performance of labor-

intensive finishing and insulation works. To confirm the effectiveness of

using the proposed method of precast-monolithic floor slab installation, the

operation of two floor slabs was modeled in the LIRA SAPR computing

complex - the proposed reinforced concrete innovative slab and a solid

reinforced concrete slab. Having analyzed the calculated forces,

deformations and the corresponding consumption of reinforcement and

concrete, comparative indicators were obtained for the proposed innovative

slab and for a typical solid floor slab. As a result, significant savings in

material and cost have been proven.

Introduction In modern monolithic construction, the priority task is to reduce the material consumption

of the structure by applying technological methods for the rational use of materials, as well

as reducing labor costs for the entire construction period. The installation of monolithic

reinforced concrete floor slabs is an important and necessary stage in the construction life

cycle. The disadvantage of such an floor slab is the high own weight of the structure.

Because of this, it is required to strengthen all the supporting elements of the building

frame. This need leads to an increase in the consumption of materials, labor costs, and, as a

result, an increase in financial costs for construction. Based on this, effective constructive

*Corresponding author: [email protected]

E3S Web of Conferences 258, 09019 (2021)

UESF-2021https://doi.org/10.1051/e3sconf/202125809019

© The Authors, published by EDP Sciences. This is an open access article distributed under the terms of the Creative

Commons Attribution License 4.0 (http://creativecommons.org/licenses/by/4.0/).

and technological solutions for lightweight precast-monolithic floor slabs have been

developed recently.

For example, the use of lightweight expanded polystyrene inserts in the thickness of

reinforced concrete floor slabs leads to a decrease in their own weight and, as a result, to a

decrease in loads on floor slabs, vertical structures and foundations, which makes it

possible to reduce the material consumption of these structural elements. And the use of

permanent formwork allows you to reduce labor costs for assembly and disassembly of the

formwork. Thus, due to the use of permanent formwork and expanded polystyrene inserts,

the installed structure will immediately have an increased degree of construction readiness,

which, in its turn, will lead to savings in labor costs and other resources. The

aforementioned determines the relevance of further scientific research and pre-design

developments aimed at saving resources in the installation of floor slabs by applying

innovative solutions in their constructive and technological directions.

To replace prefabricated housing construction, in the last two to three decades,

monolithic reinforced concrete frame structural systems have become most widespread due

to their increased rigidity and ease of production of reinforced concrete work in collapsible

industrial formwork systems directly at the construction site [1]. At the same time, such

technologies also have a number of significant disadvantages associated, first of all, with

their increased labor intensity and long terms of work completion. Therefore, both in the

post-Soviet countries and in the far abroad, compromise precast-monolithic constructive-

technological systems of low-rise civil construction are becoming more widespread [2]. In

our further work, we will show the possible directions of intensification and the results of

improving the technical and economic indicators of the installation of precast-monolithic

reinforced concrete floor slabs through their research and resource-saving improvement.

After all, the share of prefabricated monolithic structures for floor slabs in the EU

countries, according to various estimates, ranges from 20% to 35% [3]. In Russia, such

floor slabs were not used at all until 2008. While such structures have a lower own weight,

higher heat and sound insulation performance, they do not require the use of powerful

lifting equipment and other associated labor costs [4]. Focusing on well-known foreign

precast-monolithic systems, such as (Fig. 1): Porotherm floor slab (Austria, hollow inserts

made of ceramic blocks); TERIVA floor slab (Poland, hollow concrete inserts, including

expanded clay concrete); YTONG floor slab (Sweden, aerated concrete blocks); Rectolight

floor slab (France, curved pressed wood inserts); FIT SLAB floor slab (Italy, stamped

plastic ribbed liners), the Russian Federation patented and is developing a domestic

innovative technology SMP MARCO [5-7].

Fig. 1. Common systems of precast-monolithic floor slabs with block inserts made of stone materials

A similar system with filling made of polystyrene concrete blocks BETOBLOK also

becomes popular. Only the absence of nearly located factories specializing in the

Russia

Marco

Sweden

Ytong

France

Rectoligt

Germany

Porotherm

Poland

Teriva

Russia

IZH 670



2

manufacture of precast elements of this system hinders the widespread use thereof. In

addition, revision and a comparative assessment of the cost of similar structures, but with

different filling materials, are required. Our suggestions on the use of inserts made of

limestone (shell rock) blocks as a local material for the construction of low-rise buildings

(Fig. 2), [8] can also be considered one of its possible improvements.

Modification thereof is in replacing the pre-fabricated precast reinforcing-formwork

block with two elements that allow their manufacture under construction conditions - a

spatial reinforcement cage and a formwork base board, on which the mentioned

reinforcement cage was mounted with a gap that provides the required thickness of the

concrete cover.

Another possible and practical way of reducing own weight of flat floor slabs in a

precast-monolithic building frame is also the replacement of a part of concrete with plastic

inserts of various shapes: balls and similar bodies of revolution (Bubble Deck technology),

rectangular parallelepipeds (NAUTILUS technology), etc. In their projects, the developers

show up to 35%, and even up to 50% savings in reinforced concrete with the resulting other

improved technical and economic indicators (cost, timing) [9, 10]. Analytical studies of

comparative strength and deformation properties of such systems in comparison with a

solid reinforced concrete slab were also carried out [11]. However, such studies in the

aforementioned work have not been brought to the level of assessing the economic

efficiency of technology implementation at specific sites.

Fig. 2. The concreting process and the basic structural diagram of the inserted floor slab with inserts

made of shell rock or polystyrene concrete blocks

Well-known Russian experts also paid attention to the listed structural systems, and

proposed to use them to replace wooden floor slabs, as the most material-intensive

structures of civil buildings, in particular, during their overhaul [12]. The authors have

Design reinforcement

2 diameters 12 А400С

Structural reinforcement 1

Structural

reinforcement



3

developed and recommended technologies for the reconstruction of floor slabs using non-

removable spherical and prismatic inserts made of plastic and expanded polystyrene,

providing a reduction in the duration of works by 18-20% with a corresponding

improvement in other economic and operational indicators. The possibility of using

lightweight structures when replacing floor slabs in reconstructed buildings is considered in

the article [13]. It is noted that this allows to reduce the load on the existing structures of

walls and foundations, as well as to reduce the material consumption of the floor slabs

themselves.

The possibility of using hollow forms in the installation of monolithic foundations is

also considered. This is how the foundation slab of the middle part of the stylobate of a

residential complex in the Moscow region was designed, where the calculation of the base

plate was carried out in the SCAD Office software package (version 21.1). Saving of

concrete was 22.3%, reinforcement - 5% [14].

Specialists of the Pridneprovsk State Academy of Civil Engineering and Architecture

under the leadership of Professor N.V. Savitsky predict a reduction in capital costs in

general by up to 40% when using square-section void-formers made of expanded

polystyrene of rationally selected shape and size [15, 16]. But this requires not only a

constructive, but also a technical and economic assessment of the inevitable complication

of the works arrangement.

After conducting a patent search, studying information from the Internet and a literary

review, partially presented here, an original construction of a flat monolithic floor slab was

synthesized and patented, which has distinctive features and a new technical result, which

consists in reducing the consumption of reinforced concrete by taking into account the

actual work of the section of such reinforced concrete structure [ 17]. The specified

technical result is achieved by the fact that the construction of a monolithic floor slab,

having an upper and lower wire mesh, located in horizontal planes, between which there are

rows of frames alternating with inserts. The space between these inserts is filled with

concrete, and the inserts themselves are made with detachable legs, consisting of at least

two parts (Fig. 3). As can be seen in this figure, the inserts are spatial volumetric bodies of

revolution, the shape of which is close to the shape of a pear.

Fig. 3. Fragment of a floor slab structure with the replacement of a part of heavy concrete with plastic

inserts



4

We also consider perspective the structures of reinforced concrete interfloor floor slabs

with permanent formwork with precast-monolithic bearing beams, between which all kinds

of inserts are placed, replacing reinforced concrete with a lighter construction material, for

example, expanded polystyrene, on top of which a thin reinforced concrete slab is then

concreted. This leads to significant savings in heavy concrete, reduction of own weight of

the floor slab, thereby reducing the calculated constant load from the floor slab, for which

the supporting structures are designed and the costs of finishing and insulation work of the

resulting ceiling surface are reduced. An example of such system is the use of permanent

formwork made of fiberboard boards with expanded polystyrene inserts or fiberboard

(arbolite) boards according to the VELOX technology (Fig. 4).

Fig. 4. VELOX - technology of low-rise civil construction

Developers and manufacturers call such slabs chip cement [18]. Similar slabs based on

wood chips can also be produced using the carbonate hardening dolomite binder developed

by our scientists [19]. In addition to saving material and labor costs during the production

of the floor slab itself, you will get a ceiling surface that usually requires only finishing,

which is certainly a more technological solution, since it does not provide for time-

consuming wet plaster or widespread cladding with gypsum plasterboard sheets. However,

this structural and technological system usually provides for the support of the floor slabs

only on the longitudinal bearing walls, i.e. is used mainly as a beam.

Its further resource-saving development, we believe, is also the use of a slab precast-

monolithic floor structure, resting upon all four sides. In this version of the system, the

combination of a monolithic reinforced concrete belt and a precast-monolithic floor slab

according to the improved VELOX technology resting upon all sides will provide a more

significant synergistic effect of saving materials, especially heavy reinforced concrete. To

solve this problem, a precast-monolithic reinforced concrete floor slab is proposed,

consisting of conjointly made slabs and beams with reinforcement, located in two directions

and forming a mesh with a side ratio of less than two. In this case, the reinforcing cages of

the beams have a triangular shape in a plane perpendicular to their longitudinal axes, and

the reinforcing mesh of the slab is connected to the reinforcing cage of each beam, which

has a triangular shape. Between the mentioned beams there are cells not filled with concrete,

which are located in the space between the beams to the slab (Fig. 5), RF patent for utility

model No. 190006 [20].

Using the proposed floor slab structure, even in the technological process of its

manufacture, it will be possible to obtain a constructive system that ensures the

performance of load-bearing, insulating and finishing functions without the need for the

subsequent implementation of most time-consuming and heavy finishing and insulation

works. This is ensured by a pre-fabricated hermetically sealed continuous permanent

To increase strength, you can add a stiffener

Concrete



5

formwork. The proposed clamps simultaneously play the role of rigid connections of

individual shields into a geometrically stable and unchangeable system [21]. Thus, the

arranged structure of the precast-monolithic floor slab will have an increased degree of

construction readiness immediately after its manufacture in one complex construction-

technological process. Consequently, the proposed technology intensifies the complex

construction process, reduces its labor intensity and cost.

It is possible to confirm the stated assumptions by means of experimental and

theoretical studies of the comparative efficiency of the presented constructive and

technological solutions for interfloor precast-monolithic floor slabs. To confirm the

advanced hypothesis about the effectiveness of the presented scientific and design

developments of precast-monolithic floor slab structures, it is necessary to simulate the

operation of two floor slabs - the original solid reinforced concrete slab and an innovative

slab with a permanent formwork and expanded polystyrene inserts. Computer modeling of

the stress-strain state with the design of the structure and principal reinforcement must be

carried out in the LIRA-SAPR computing complex; it is also necessary to perform

calculations and assess the technical and economic indicators of the proposed technologies.

Materials and MethodsTo assess the comparative effectiveness of the proposed structural and technological system

of precast-monolithic floor slabs, the problem of computer modeling of the operation of the

proposed innovative reinforced concrete precast-monolithic slab and a reinforced concrete

solid slab at the same representative object was set and solved. The computational

experiment was implemented at a specific object - a multi-storey building designed in the

city of Sevastopol. The designed sectional-type residential building, 9-storey, with one

entrance, frame with the outer walls filled with foam concrete blocks, with a technical

underground and a flat unexploited roof. The building has a complex shape, close to a

rectangular one in plan with dimensions in the axes of 37.2×22.5 m (Fig. 6). The building is

38.72 m high.

The innovative floor slab is structurally a bearing ribbed system with mutually

perpendicular ribs of the same height and a continuous thin horizontal slab on top. Such

floor slab is formed using permanent formwork and expanded polystyrene inserts on it (Fig.

5).

The thickness of the shelf of the floor slab was determined subject to several conditions.

The first of these was to ensure the required strength of the shelf itself with a minimum use

of resources. Depending on the purpose of the building and premises, the nature of the

loads that are transmitted to the floor slab changes.

The second prerequisite was the provision of normalized concrete cover thicknesses for

the shelf reinforcement. On the other hand, the thickness of the shelf had to be reduced to

make the structure as lightweight as possible. Based on this, one can come to the statement

that the thickness of the shelf should be such that the reinforcement lies in one layer in two

directions, i.e. it is reinforced with one mesh.



6

1 - 1

Assembly A

Fig. 5. Improved precast-monolithic reinforced concrete floor slab according to the basic VELOX

technology: 1 - precast-monolithic slab; 2 - monolithic beam; 3 - reinforcement; 4 - reinforcing cages;

5 - reinforcing mesh of the slab; 6 - trapezoidal expanded polystyrene inserts; 7 - permanent plank

formwork; 8 - position clamps of the lower reinforcement; 9 - self-tapping screws; 10 - tongue-and-

groove connection of wood concrete boards

Fig. 6. Typical floor plan of the designed building

The floor slabs were calculated for the effect of calculated permanent, long-term and

short-term loads, special loads, as well as combinations thereof. The spatial design of the

floor slab is statically indeterminate. The calculation was carried out using a computational

complex (PC LIRA-SAPR) using the finite element method. Further, permanent, temporary

and short-term loads per 1 m2 of a solid floor slab were collected, and also the own weight

of the slab was taken into account. The loads per 1 m2 of the innovative slab were assumed

to be the same as for a solid base slab.

ResultsThe results of processing design schemes, displacement isofields, bending moments,

required reinforcement for two slab options are summarized and presented in a tabular form

Assembly A



7

(Table 1), and a summary of material consumption and the cost thereof are presented in

Table. 2, fig. 7. Master Dogoshapko I.M. took part in the calculations.

Table 1. Comparative characteristics of computer models and the results of calculations for rational

design of the considered options for interfloor structures

Table 1 (continued)1 2

Bending moment My

Solid monolithic reinforced

concrete slab

Proposed slab with expanded polystyrene

inserts and permanent formwork

1 2

Floor Slab Isometric Models

Deformed floor slabs schemes

Isofields of slab displacements along the Z axis

Bending moment Mx



8

Lower reinforcement area along X

Lower reinforcement area along Y

Upper reinforcement area along X

Upper reinforcement area along Y

Table 2. Comparison of material consumption based on the results of modeling the operation of the



9

considered competing floor structures

Reinforcement A500Cost,

thousand

Rub.

Concrete

B25,

m3

Expanded

polystyrene,

thousand Rub.

Permanent

formwork, thousand

rubles

Cost,

thousand

Rub.Diameter Tons

1 2 3 4 5 6 7 8

Solid slab

Lower reinfor-

cement

Ø-10

Ø-12

0.73

13.83

30 295

549 051

169 - - 845000Upper reinfor-

cement

Ø-10Ø-12

Ø-16

0.050.97

2.27

2 07538 509

88 984

Strengthe-

ningØ-18 1.06 41 552

Total - 18.91 750466 169 - - 845.000

Total floor

slab- - - - - - 1 595 466

Innovative slab

Upper mesh Ø-8 3.19 131 855

89.7 36 180285 25

8448 500

Reinforce-

ment of frameworks

Ø-6

Ø-10Ø-12

0.43

0.744.26

19 384

38 515207 053

Strengthening Ø-18 1.06 41 552

Total - 9.68 438.359 89.7 36 180285 25

8448 500

Total floor

slab- - - - - - 1 208 297

Fig. 7. Material consumption histograms

DiscussionAs can be seen from the presented results, the proposed innovative design of precast-

monolithic floor slab provides significant savings in material resources: steel - by 26% and



10

concrete mix by 47%. The results obtained do not go beyond the limits noted by other

researchers and designers [9, 10]. In value terms, the savings on materials are 387 thousand

rubles per floor slab. Consequently, the proposed design will be more technologically

advanced in production compared to the traditional solid floor slab. Additionally, the cost

items not taken into account when modeling the economic effect are to reduce the labor

intensity and cost of subsequent finishing work. Reduction of own weight of the structure

of the interfloor floor slabs entails a decrease in other material costs - for the installation of

foundations and load-bearing elements of the frame. In addition, a reduction of own weight

of this frame has a positive effect on a decrease in inertial seismic loads, which is important

for earthquake-resistant construction in Crimea.

SummaryThis is a scientifically substantiated and patented Russian technology for the installation of

precast-monolithic reinforced concrete floor slabs with expanded polystyrene inserts in a

permanent formwork. By modeling two competing design solutions in the LIRA-SAPR

computing complex - monolithic and precast-monolithic floor slabs, we demonstrate a

significant saving in materials when using an innovative solution: concrete - almost 47%,

metal - 26%, which in value terms is 24.6%. Consequently, the developed technology of the

floor slab installation can be recommended as a resource-saving one for further study and

use in construction practice.

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Improving the manufacturability of floor slabs by pre